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THE CONDOR 

A Bi-MontHly Magazine of 
Western OrnitHology 



Volume XXII November-December. 1920 Number 6 

[Issued December 4, 1920] 



THE WING CLAW IN SWIFTS 
By ALEXANDER WETMORE 

IN a paper on "The Claws and Spurs on Birds' Wings", Jeffries (Proc. 
Boston Soc. Nat. Hist., xxi, 1881, pp. 301-306) recorded in a tabular survey 
of the occurrence of wing claws in birds that the wing claw was present in 
the Old World swifts of the genus Micropus and that no wing claw was found 
in the Chimney Swift (Chaetura pelagica). 

A brief examination of a series of Chimney Swifts showed the present 
writer that this species possessed well developed wing claws so that what had 
appeared to be another character separating the two subfamilies of spiny-tailed 
and soft-tailed swifts proved invalid. Opportunity was taken in this connec- 
tion to examine for this character all of the species of swifts available in the 
collections of the United States National Museum with results that proved of 
some interest. In all, 48 species belonging to 12 genera were available, as in- 
dicated in the following list. 

In arranging my notes on these swifts I have encountered difficulty in the 
arrangement, treatment and choice of names to be used; for there have been 
varying opinions as to the limits of groups and the allocation of subspecies, 
while no recent comprehensive monograph has covered the entire family in a 
manner wholly satisfactory. In general the arrangement of the genera is that 
given by Mr. Ridgway (Bull. 50, U. S. Nat. Mus., v, 1911, pp. 685-686), with 
the inclusion of Tachynautes (Oberholser, Proc. U. S. Nat. Mus., xxvm, 1905, 
p. 860), while the majority of the species are taken as they stand in Sharpe's 
Hand-List (vol. n, 1900, pp. 89-96). The genus Collocalia is based on Oberhol- 
ser 's monograph of this group (Proc. Acad. Nat. Sci. Phila., vol. 58, 1906, pp. 
177-212), save that the treatment of Collocalia fuciphaga, C. vestita, and C. 
lovi is that of Streseman (Verh. Orn. Ges. Bayern, Bd. xn, 1914, pp. 1-12). 
New species and subspecies not covered by these authors are included in what 
appears to be their logical positions. The writer does not venture to say that 



198 



THE CONDOR 



Vol. XXII 



the combination produced is a happy one, but believes that it will at least en- 
able others to determine what birds he has seen. 



Micropus melba (Linnseus) 
Micropus aequatorialis (Muller) 
Micropus apus (Linnseus) 
Micropus pacificus (Latham) 
Micropus horus (Heuglin) 
Micropus af finis (J. E. Gray) 
Micropus subfurcatus (Blyth) 
Micropus andicola (Lafresnaye and 

D'Orbigny) 
Micropus myoptilus (Salvadori) 
Aeronautes melanoleucus (Baird) 
Panyptila sanctihieronymi Salvin 
Panyptila cayanensis (Gmelin) 
Tachynautes parvus (Lichtenstein) 
Tachornis infumntus (Sclater) 
Tachornis phoenicobius Gosse 
Hirundapus celebensis (Sclater) 
Hirundapus caudacutus (Latham) 
Hirundapus giganteus (Temminck) 
Mearnsia picina (Tweeddale) 
Streptoprocne zonaris (Shaw) 
Streptoprocne semicollaris (Saussure) 
Nephoecetes niger (Gmelin) 
Cypseloides brunneitorques (Lafres- 
naye) 
Cypseloides cherriei Ridgway 
Chaetura pelagica (Linnaeus) 
Chaetura vauxi (Townsend) 
Chaetura richmondi Ridgway 
Chaetura gaumeri Lawrence 
Chaetura acuta (Gmelin) 
Chaetura poliura (Temminck) 
Chaetura cinereiventris Sclater 
Chaetura stictilaema (Reichenow) 
Chaetura leucopygialis (Blyth) 



Collocalia innominata Hume 
Collocalia ocisia Oberholser 
Collocalia fuciphaga fuciphaga 

(Thunberg) 
Collocalia fuciphaga vanikorensis 

(Quoy and Gaimard) 
Collocalia fuciphaga amelis Oberhol- 
ser 
Collocalia fuciphaga unicolor (Jer- 

don) 
Collocalia vestita vestita (Lesson) 
Collocalia vestita mearnsi Oberholser 
Collocalia vestita elaphra Oberholser 
Collocalia vestita aenigma Riley 
Collocalia origenis Oberholser 
Collocalia lowi lowi (Sharpe) 
Collocalia lowi palawanensis Strese- 

man 
Collocalia inopina Thayer and Bangs 
Collocalia thespesia Oberholser 
Collocalia francica townsendi Ober- 
holser 
Collocalia francica inexpectata Hume 
Collocalia francica germani Oustalet 
Collocalia troglodytes G. R. Gray 
Collocalia marginata Salvadori 
Collocalia linchi affinis Beavan 
Collocalia linchi elachyptera Oberhol- 
ser 
Collocalia linchi isonota Oberholser 
Collocalia linchi oberholseri Strese- 

man 
Collocalia dodgei Richmond 
Collocalia esculenta (Linnaeus) 
Collocalia bartschi Mearns 



The wing claw in the Micropodidae is placed near the tip of the thumb or 
pollex and is concealed beneath the feathers that form a sharp anterior margin 
on the wing at that point. The large series of birds studied were examined 
under a binocular dissecting microscope with a magnification of eight diame- 
ters. The use of this instrument left both hands free to manipulate the bird, a 
necessary arrangement, as the claw is small and at times difficult to locate 
among the feathers. The claw in general is blackish or dusky in color, and is 
comparatively long, with the tip recurved in a slight hook. It is attached 
rather loosely and may be removed easily, but where a claw has been broken 
away, its former location is plainly indicated by a scar. The form of the claw 
varies to some extent, and in abnormal individuals it may degenerate into a 
short knob with slight projection. 

In all of the swifts examined wing claws were normally developed save in 
one group of species belonging to the genus Collocalia. In the various subspe- 
cies of C. linchi the wing claw was normal in some cases, rudimentary in oth- 
ers, and occasionally was absent on one or both wings. The same was true in a 



Nov., 1920 THE WING CLAW IN SWIFTS 199 

series of nine C. esculenta. The wing claw was much reduced in seven C. 
troglodytes and in one specimen was absent on one wing. In Collocalia mar- 
ginata no trace of a wing claw was found in an examination of both wings of 
nine individuals, and wing claws were absent also in the type of C. dodgei (the 
only specimen of this species seen). Wing claws were present in the type spe- 
cimen of C. bartschi. In the other species of Collocalia available (C. innominata, 
ocista, fuciphaga, vestita, origenis, lowi, inopina, thespesia, and francica) wing 
claws were present on both wings, though occasionally they were small and 
often were curled and twisted. In one individual of C. f. amelis the wing claw 
on the right wing grew from the base of the pollex instead of the tip. The 
wing claw may possibly develop rather late in the growth of the young bird, 
as I found it absent entirely in three nestlings of Collocalia I. isonota, but pres- 
ent in both wings in a fully fledged young of Collocalia origenis. It is inter- 
esting to note that in the Tree Swifts (Hemiprocnidae), a family considered to 
be closely allied to the true swifts (Micropodidae), no wing claw is present. 
The species examined include Hemiprocne longipennis, mystacea, comata, wal- 
lacei and perlonga. 

While it has proved that the wing claw in the Micropodidae is not a char- 
acter of taxonomic value it has been interesting to note its persistence in gen- 
eral and its absence in certain cases. The section of edible nest swiftlets, cover- 
ing the small blue-black species with more or less white in the plumage, seems 
to be on the way to discarding the wing claw, though here the loss is not as 
yet universal and may vary in one species- or even in one individual. From the 
present evidence I am inclined to consider the wing claw in swifts as an archaic 
trait that is no longer of value and is on the way to being lost. There is no 
evidence at hand to show that the claw is used by these birds in attaching or 
climbing on the rough surfaces on which they rest. No wear is evident on the 
wing claw itself, nor is there abrasion on the feathers concealing it. 

From a limited amount of material (all in dried skins) it seems that the 
wing claw does not appear until the young bird is well feathered, so that it is 
not of use in a juvenile stage. This, however, should be carefully verified in 
fresh material for, if this claw be considered an archaic character, it is strange 
if it does not appear very early in the life of the individual. 

Biological Survey, Washington, D. C, May 26, 1920.